1. Field of the Invention
The present invention relates to a photometric apparatus, such as a spectrophotometric apparatus, and more particularly to a photometric apparatus having an ultraviolet (UV) light source.
2. Description of the Related Art
There has been known a spectrophotometric apparatus which is equipped with a UV light source, such as a deuterium lamp, and designed to spectrally disperse light emitted from the light source by a wavelength dispersive element, and detect light components of respective wavelengths after undergoing interaction with a sample to obtain an intensity distribution on a per wavelength basis so as to analyze the sample quantitatively and/or qualitatively, wherein oxygen which exhibits an absorption peak in a deep UV region is eliminated from a light path to allow measurements to be accurately performed even on a shorter wavelength side of the deep UV region. This type of spectrophotometric apparatus is provided with a mechanism for supplying replacement gas (i.e., inert gas, such as nitrogen, helium or argon gas), to replace an internal atmosphere of the apparatus with the gas (hereinafter referred to as “gas replacement operation”), and/or a mechanism for providing a vacuum to an internal space of the apparatus using a vacuum pump or the like (hereinafter referred to as “vacuuming operation”). These mechanisms are activated when a measurement in the deep UV region (hereinafter referred to as “deep UV measurement”) is performed, so as to purge oxygen from the internal space of the apparatus, as disclosed in Japanese Patent Laid-Open Publication No. 11-211566 (paragraphs [0022], [0023]).
Generally, UV light reacts with oxygen in the atmosphere to generate ozone. This ozone has adverse effects on rubber materials and various other materials in the long and medium terms, as is commonly known. A photometric apparatus equipped with a UV light source also involves ozone generation around the light source, and some internal parts of the photometric apparatus, such as parts of an optical-element driving mechanism, are likely to be adversely affected by the ozone. Ozone-induced corrosion in the internal parts will contribute to deterioration in durability and reliability of the apparatus.
Particularly, in the type of photometric apparatus designed to perform the deep UV measurement, the internal space including the light path is kept in a hermetically sealed state relative to an outside environment to efficiently carry out the gas replacement or vacuuming operation, which is required for the deep UV measurement. Thus, ozone gas generated around the light source is likely to fill the inner space of the apparatus during measurements in UV wavelength regions other than the deep UV region (these measurements will hereinafter be referred to as “non-deep UV measurements”). This accelerates corrosion in the internal parts, even though this problem can be avoided as long as the deep UV measurement is performed, because oxygen causing ozone generation is purged through the gas replacement or vacuuming operation during deep UV measurement. While this photometric apparatus may be designed to extend, to the non-deep UV measurements, the vacuuming or gas (e.g., nitrogen gas) replacement operation for the deep UV measurement, measurement or running costs will be extremely increased although the internal parts can be protected from the ozone-induced corrosion. Thus, in terms of economical efficiency, it is undesirable to operate the vacuum pump or supply the replacement gas when there is no need for the deep UV measurement, only for the purpose of diluting or eliminating ozone.